1. Field of the Invention
The present invention concerns an illumination apparatus used by connecting an illumination head in which one or more light emitting devices are connected in a power supply circuit to a power source device, as well as an illumination head and a power source device used therefor.
2. Statement of Related Art
In illumination apparatus for lighting up a plurality of LED arranged, for example, in an illumination head, since the lightness is lowered when the current supplied to individual LED as light emitting device is lower than the rated current thereof, and undesired effects are given on the working life when the current is higher, power of the power source is set such that LED can be lit by the supply of the rated current.
For example, as shown in FIG. 3(a), in a case where LED 33, - - - each with a forward rated current of 20 mA are connected by the number of ten in parallel in a power supply circuit 32 of an illumination head 31, a current at 200 mA is supplied to the power supply circuit 32.
Then, the power source device capable of controlling the current supply in accordance with the number of LED to be lit such that a rated current can be supplied to individual LED 33, 33, - - - even when the number of LED 33, 33, - - - to be lit is changed in recent years (refer to JP-A-No. 2000-6466).
However, the power source device of the type described above controls the current depending on the number of LED 33, 33, - - - to be lit in a case of connecting a specified illumination head 31, and can not control the current in accordance with the specification in a case of using a power source device for illumination heads of different specifications.
That is, since the type of the illumination heads using light emitting devices such as LED are versatile and specifications of them such as the connection method of LED to the power supply circuit (for example parallel or series connection), the number of LED and the rating for individual LED are different on every illumination heads, this results in a problem that a power source device or a current controller has to be desired to be designed and manufactured in accordance with the illumination heads.
For example, in a case where the rated current for individual LED attached to the illumination head 31 is normalized as 20 mA, when LED 33, 33, - - - are connected in parallel by the number of ten as described above, it is necessary to supply 200 mA current to the power supply circuit 32. In a case where LED 33, 33, - - - are connected in series by the number of 10, it may suffice to supply 20 mA current to the power supply circuit 34, in a case where LED 33, 33, - - - connected by the number of 10 in series are connected in parallel by three rows, it is necessary to supply 60 mA current to the power supply circuit 35.
Accordingly, while the power source device has been designed in accordance with the specifications for respective illumination heads 31, if a power source device of an identical rating can be used irrespective of the specification of the illumination head 31, this can save the troubles of designing and manufacturing the device on every individual illumination heads 31 to remarkably decrease the manufacturing cost.
In view of the above, it is a technical subject of the present invention to use a power source device of an identical rating irrespective of the specification of the illumination head and which can light up individual light emitting devices of the illumination head connected to the power source device at a rated current.